File - Canadian Wayfarer Association

We used to use a block with a becket at the end of the boom - which
required one less slide - but I find I prefer the system diagrammed
above with the end system that I just finished laying onto my scanner
with the result at left:
You can probably see how thin that sheet is - it doesn't bother my
hands but then I
• have fairly tough hands
• cleat and uncleat the mainsheet hundreds of times per race
The snap shackle is fairly permanently attached to the aftermost Ubracket
on the boom but in last year's drifters on the Sunday of the
Midwinters, it was nice to be able to unsnap it from the boom.
This takes one purchase and a lot of rope pulling out of the system for
places such as the leeward mark! And a thin sheet runs much more
freely through its blocks, which faster and sometimes safer!
The Swivel Block & Cleat Assembly
As luck would have it, I inherited what I believe to be the perfect swivel block assembly. Made
by Barton, it has a short, low-rise plate that attaches the metal cam cleat to its base. Much as I
love Harken stuff of almost every description, I have dumped at least twice when using a
borrowed boat that had their standard high-rise swivel cleat. The problem was that, during a
tack, the sheet cleated itself on the Harken swivel whereas my Barton swivel takes a conscious
effort to cleat - i.e. I have to reach down, or push on the sheet with one foot, to make it cleat.
If find this easier to do than to explain, and for me, it is certainly much safer (and drier!)
I believe the glass boats tend to come with a spot provided for the swivel mount at the aft end
of the centreboard box. If I had a glass boat, I would not use this location since it's too low for
my taste. And above all, it's too far aft - considering that I go aft of the mainsheet each time I
tack, and that the further aft I go, the more transom drag I get.
1.3.7 Mainsail shape and trim 16
The mainsail has a very important role to play in the development of power from the whole rig.
This stems not only from its function as the windward part of the slot between genoa and main,
but also from its sheer size. Correct setting up and control are therefore necessary to get the
most speed out of the sail. Particular care has to be taken with the mainsheet tension because it
is very easy to oversheet and stall the air flow coming off the leech. This usually occurs when
beating or reaching. So do remember that as the air flows over the sail’s windward and leeward
surfaces, it forms a pressure gradient which creates a leeward going force at right angles to the
sail’s surface. Obviously the bulk of this force is in the leeward front sections of the sail, but if
the leech is too tight, some of it will actually be facing backwards to create drag. This not only
decreases forward movement but increases sideways and heeling forces. In such a case, the
leeward air will refuse to conform to the sail’s exit curve. As the lee-ward air flow breaks away,
the sail stalls, resulting in a dramatic loss of power and speed. This explains that sudden loss of
speed in fluky or gusty conditions when the sail cannot cope with the variations in the speed of
the air flowing across it, and it explains why rigs must be capable of adjustment.
16 slightly spiffed-up version of an article that Mike McNamara wrote for the May 1990 Whiffle
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